• I am a passionate researcher who focuses on and enjoys research

    Research Scientist @ Laboratory for Information and Decision Systems (LIDS), Massachusetts Institute of Technology (MIT), United States

    Adjunct Professor @ Department of Civil & Environmental Engineering, University of Massachusetts Lowell, United States
    Google Scholar, ORCID: 0000-0001-5716-3853 Email: he dot zb at hotmail dot com

    Prior to joining MIT, I was a tenured full professor at Beijing University of Technology, China. As a principal investigator, I have secured funding exceeding $1 million for national-level (key) projects. I have published over 160 academic papers, including 40+ papers in the prestigious journal series of Transportation Research and IEEE Transactions, with total citations >6000, i10-index=80 and H-index=37. Annual citations from 2017 to 2024 continue increasing: 85-229-413-691-740-1034-1132-1440

    I am an IEEE senior member and was listed as World’s Top 2% Scientists (Ranking 147 in Transportation & Logistics). I serve as a Senior Editor for IEEE Transactions on Intelligent Transportation Systems, a Deputy Editor in Chief for IET Intelligent Transport Systems, an Associate Editor for IEEE Transactions on Intelligent Vehicles, a Handling Editor for Transportation Research Records, an Editorial Advisory Board member for Transportation Research Part C, etc.

    Research Interests

    As a seasoned researcher, my work lies at the intersection of transportation, systems engineering, and artificial intelligence, with a focus on topics such as

    • data-driven modeling and intelligent vehicle-enabled congestion solutions,
    • learning-based sensing and prediction of traffic congestion and travel demand, and
    • sustainability-oriented optimization in transportation.

    Research Interests

    • Journal of Transportation Engineering and Information (in Chinese), Editor-in-Chief
    • IEEE Transactions on Intelligent Transportation Systems, Senior Editor
    • IET Intelligent Transport Systems, Deputy Editor-in-Chief
    • Transportation Research Part C: Emerging Technologies, Editorial Advisory Board member
    • Transportation Research Record, Handling Editor
    • International Journal of Crowd Science, Associate Editor
    • Chair, SIG C1 (Traffic Theory and Modelling/Optimization and Traffic Flow), World Conference on Transport Research Society (WCTRS)
    • IEEE Intelligent Transportation Systems Conference (ITSC), Associate Editor, 2018-to date: 21st (US), 22nd (New Zealand), 23rd (Greece), 24th (US), 25th (China), 26th (Spain), 27th (Canada),
    • IEEE Intelligent Vehicles Symposium (IV), Associate Editor (Korea, 2024), Session Chair (China, 2018)
    • IEEE, Senior Member
    • IEEE Access, Associate Editor (2017.10-2019.10), Outstanding Award (top 5%)
    • International Journal of Intelligent Transportation Systems Research, Associate Editor (2021.3-2024.3)
    • IEEE International Conference on Intelligent Transportation Engineering, Award Chair (2020-2021)
    • Forum on Integrated and Sustainable Transportation Systems, Delft, The Netherlands, Associate Editor, 2020
    • 19th COTA International Conference of Transportation Professionals, 2019, Nanjing, China, Area Editor: Traffic Operations, Control and Management

    Guest Edited Issues

    • Space Weather, Special Issue: Impact of Space Weather Events on Transportation System, 2023
    • IET Intelligent Transport Systems, Modelling, Operation and Management of Traffic Mixed with Connected and Automated Vehicles, 2021
    • Transportation Research Part D: Transport and Environment, Special Issue: Shared Mobility and Environment, 2020
    • Transportation Research Part C: Emerging Technologies, Special Issue: Emerging Methods for Data-driven Urban Transportation and Mobility Modeling, 2019
    • Transportmetrica A: Transport Science, Special Issue: Methodological Advancements in Understanding and Managing Urban Traffic Congestion, 2018
    • Journal of Intelligent Transportation Systems, Special Issue: Vehicle Sensor Data-based Transportation Research, 2018

    Published Journal Papers

    First-author papers have been published in many journals, including

    • Transportation Research Part A
    • Transportation Research Part B
    • Transportation Research Part C
    • Transportation Research Part D
    • Computer-Aided Civil and Infrastructure Engineering
    • IEEE Transactions on Intelligent Transportation Systems
    • IEEE Transactions on Intelligent Vehicles
    • Transportmetrica B: Transport Dynamics
    • ASCE Journal of Transportation Engineering
    • Journal of Intelligent Transportation Systems
    • Transportation Letters
    • Proceedings of ICE-Transport
    • Physica A: Statistical Mechanics and its Applications
    • International Journal of Modern Physics C, etc.

    Corresponding-author papers

    • Transportation Research Part A
    • Transportation Research Part C
    • Transportation Research Part D
    • IEEE Transactions on Intelligent Transportation Systems
    • Transportation
    • Transport Policy
    • Journal of Transport Geography
    • Information Fusion
    • Transportmetrica A: Transport Science
    • Transportmetrica B: Transport Dynamics
    • IET Intelligent Transport Systems
    • Transportation Research Record
    • International Journal of Sustainable Transportation
    • International Journal of Modern Physics B
    • International Journal of Modern Physics C
    • Physica A: Statistical Mechanics and its Applications, etc.
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  • Publications (by selected topics)

    1. Solo Author | "Simple" Series
    2. Data-driven Traffic Modeling | Microscopic Traffic Modeling | Traffic Stabilization | Autonomous Intersection | Intelligent Vehicles
    3. Time-space Traffic Diagram | Sensing: Mapping to Cells | Traffic State Estimation
    4. Day-to-day Route Choice | Route Guidance | Network Equilibrium
    5. Sustainability-oriented Optimization
    6. Resilience
    7. Large Language Models | Machine Learning and Prediction
    8. Data Analysis
    9. Policy
    10. Review and Perspectives
    11. Others (Selected)
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  • 0. Latest Publications (2025/Online/Accepted)

    • Environmental impacts and emission reduction methods of vehicles equipped with driving automation systems: An operational-level review, Transportation Research Part C, 2025
    • Identifying users transferring between transportation modes: A stable matching approach, IEEE Transactions on Intelligent Transportation Systems, 2025
    • Platoon or Individual: An Adaptive Car-following Control of Connected and Automated Vehicles, Chaos Solitons & Fractals, 2025
    • Brain Driving: Personalizing Vehicle Speed with DR-EEG Decoding and Situational Embeddings, IEEE Transactions on Intelligent Vehicles, online
    • Exploring the relationship between built environment and bike-sharing demand: Does the trip length matter? Transportation Planning and Technology, online
    • On the precise quantification of the impact of a single discretionary lane change on surrounding traffic, arXiv:2407.18557, 2024
    • A Survey on Large Language Model-empowered Autonomous Driving, arXiv.2409.14165. 2024
    • AI-Driven Day-to-Day Route Choice, arXiv.2412.03338, 2024
    • NeuralMOVES: A lightweight and microscopic vehicle emission estimation model based on reverse engineering and surrogate learning, arXiv:2502.04417, 2025
    • Estimating city-wide operating mode distribution of light-duty vehicles- A neural network-based approach, arXiv: 2503.22118, 2025
    • Identifying public transit deserts: A travel demand-independent persistent homology-based method, Transportation Safety and Environment, 2025

    1. Solo Author

    • Refining time-space traffic diagrams: A simple multiple linear regression model, IEEE Transactions on Intelligent Transportation Systems, 2024
    • Portraying ride-hailing mobility using multi-day trip order data: A case study of Beijing, China, Transportation Research Part A, 2021 (2022 Key innovation in Transportation Sector, Ministry of Transport, China)
    • Spatial-temporal fractal of urban agglomeration travel demand, Physica A, 2020
    • Cooperative driving and a lane change-free road transportation system, Chapter of IET Book Traffic Information and Control, 2020
    • Research based on high-fidelity NGSIM vehicle trajectory datasets: A review. DOI: 10.13140/RG.2.2.11429.60643, 2017

    1. "Simple" Series

    • Refining time-space traffic diagrams: A simple multiple linear regression model, IEEE Transactions on Intelligent Transportation Systems, 2024
    • Mapping to cells: a simple method to extract traffic dynamics from probe vehicle data, Computer-Aided Civil and Infrastructure Engineering. 2017
    • A simple nonparametric car-following model driven by field data. Transportation Research Part B, 2015

    2. Data-driven Traffic Modeling

    • A simple nonparametric car-following model driven by field data. Transportation Research Part B, 2015
    • On the impact of prior experiences in car following models model development, computational efficiency, comparative analyses and extensive applications, IEEE Transactions on Cybernetics, 2023
    • A data-driven lane-changing model based on deep learning, Transportation Research Part C, 2019

    2. Microscopic Traffic Modeling

    • The impact of a single discretionary lane change on surrounding traffic: An analytic investigation, IEEE Transactions on Intelligent Transportation Systems, 2023
    • Empirical validation of vehicle type-dependent car-following heterogeneity from micro- and macro-viewpoints, Transportmetrica B, 2019
    • A new car-following model from the perspective of visual imaging. International Journal of Modern Physics C, 2015
    • A discrete-flow form of the point-queue model, IEEE International Transportation Conference (ITSC), 2015, Spain
    • A flexible traffic stream model and its three representations of traffic flow, Transportation Research Part C, 2017
    • An anisotropic continuum model and its calibration with an improved monkey algorithm, Transportmetrica A, 2017

    2. Traffic Stabilization

    • A jam-absorption driving strategy for mitigating traffic oscillations, IEEE Transactions on Intelligent Transportation Systems, 2017
    • Heterogeneous traffic mixing regular and connected vehicles: Modelling and stabilization, IEEE Transactions on Intelligent Transportation Systems, 2019
    • Cooperative Driving Strategies of Connected Vehicles for Stabilizing Traffic Flow, Transportmetrica B, 2020
    • A new reinforcement learning-based variable speed limit control approach to improve traffic efficiency against freeway jam waves, Transportation Research Part C, 2022
    • Emissions-reduction strategy for connected autonomous vehicles on mixed traffic freeways, Physica A, 2024
    • String stability analysis of connected vehicular systems based on car-following model, ASCE Journal of Transportation Engineering, Part A: Systems, 2021

    2. Autonomous Intersection

    • Erasing lane changes from roads: A design of future intersections, IEEE Transactions on Intelligent Vehicles, 2018
    • Cooperative driving and a lane change-free road transportation system, Chapter of IET Book Traffic Information and Control, 2020
    • Pedestrian shuttle service optimization for autonomous intersection management, Transportation Research Part C, 2024
    • Is All-Direction Turn Lane a Good Choice for Autonomous Intersections? A Study of Method Development and Comparisons, IEEE Transactions on Vehicular Technology, 2023

    2. Intelligent Vehicles

    • Optimal toll design problems under mixed traffic flow of human-driven vehicles and connected and autonomous vehicles, Transportation Research Part C, 2021
    • Estimation of lane-level travel time distributions under a connected environment, Journal of Intelligent Transportation Systems, 2021
    • Platoon or Individual: An Adaptive Car-following Control of Connected and Automated Vehicles, Chaos Solitons & Fractals, 2025
    • Dynamic lane changing trajectory planning for CAV: A multi-agent model with path preplanning, Transportmetrica B, 2022
    • Exploring the impact mechanism of communicating information on the perturbation propagation, Transportmetrica A, 2024
    • Modeling the mixed traffic capacity of minor roads at a priority intersection, Physica A, 2024
    • A mixed traffic car-following behavior model, Physica A, 2023
    • Safety rule-based cellular automaton modeling and simulation under V2V environment, Transportmetrica A, 2021
    • Digital Twin Empowered Mobile Edge Computing for Intelligent Vehicular Lane-Changing, IEEE Network, 2021

    3. Time-space Traffic Diagram

    • Refining time-space traffic diagrams: A simple multiple linear regression model, IEEE Transactions on Intelligent Transportation Systems, 2024
    • Constructing spatiotemporal speed contour diagrams: using rectangular or non-rectangular parallelogram cells, Transportmetrica B, 2019
    • Estimating carbon dioxide emissions of freeway traffic: a spatiotemporal cell-based model, IEEE Transactions on Intelligent Transportation Systems, 2020
    • From rectangle to parallelogram: An area-weighted method to make time-space diagrams incorporate traffic waves, Digital Transportation and Safety, 2024
    • Visualizing traffic dynamics based on floating car data, ASCE Journal of Transportation Engineering, 2017
    • Learning traffic as images: A deep convolutional neural network for large-scale transportation network speed prediction, Sensors, 2017
    • Probe data-driven travel time forecasting for urban expressways by matching similar spatiotemporal traffic patterns. Transportation Research Part C, 2017

    3. Sensing: Mapping to Cells

    • Network-wide identification of turn-level intersection congestion using only low-frequency probe vehicle data, Transportation Research Part C, 2019
    • Mapping to cells: a simple method to extract traffic dynamics from probe vehicle data, Computer-Aided Civil and Infrastructure Engineering. 2017

    3. Traffic State Estimation

    • TSR-GAN: Generative Adversarial Networks for Traffic State Reconstruction with Trajectory Data, Physica A, 2022
    • Real-time estimation of freeway travel time with recurrent congestion based on sparse detector data. IET Intelligent Transport Systems. 2018
    • A stochastic extension of Newell’s “three-detector method". Journal of Transportation Research Board, 2012

    4. Day-to-day Route Choice

    • Investigating day-to-day route choices based on multi-scenario laboratory experiments. Part I: route-dependent attraction and its modeling, Transportation Research Part A, 2023
    • Investigating day-to-day route choices based on multi-scenario laboratory experiments. Part II: A route-dependent attraction-based stochastic process model, Communications in Transportation Research, 2024
    • Day-to-day rerouting modeling and analysis with absolute and relative bounded rationalities, Transportmetrica A. 2018
    • An analyzable agent based framework for modeling day to day route choice, Transportmetrica A, 2022
    • A day-to-day route choice model based on travelers' behavioral characteristics, 9th International Conference of Traffic and Transportation Studies, Shaoxing, 2014

    4. Route Guidance

    • A traffic-condition-based route guidance strategy for a single destination road network. Transportation Research Part C, 2013
    • A self-regulation traffic-condition-based route guidance strategy with realistic considerations: overlapping routes, stochastic traffic and signalized intersections, Journal of Intelligent Transportation Systems, 2016
    • Effectiveness of GRIPs in alleviating traffic congestion, Proceedings of ICE-Transport, 2016
    • Data-based sorting algorithm for variable message sign location, Journal of Transportation Research Board, 2017

    4. Network Equilibrium

    • A multi-modal network equilibrium model considering captive travelers and mode correlation, Transportation, 2024
    • A dynamic user equilibrium model for multi-region macroscopic fundamental diagram systems with time-varying delays, Transportation Research Part B, 2020
    • Selfish routing equilibrium in stochastic traffic network: A probability-dominant description, PLoS ONE, 2017
    • An N-path logit-based stochastic user equilibrium model, IEEE Access, 2018
    • A train operation diagram-based equilibrium model for an urban rail transit network with transfer constraint. ASCE Journal of Transportation Engineering, Part A: Systems, 2020

    5. Sustainability-oriented Optimization

    • Planning dynamic wireless charging infrastructure for battery electric bus systems with the joint optimization of charging scheduling, Transportation Research Part C, 2024
    • A robust approach to integrated wireless charging infrastructure design and bus fleet size optimization, Computers & Industrial Engineering, 2022
    • Optimal design of community shuttles with an adaptive-operator-selection-based genetic algorithm, Transportation Research Part C, 2021
    • Optimal timetable development for community shuttle network with metro stations. Transportation Research Part C, 2015
    • Demand responsive service-based optimization on flexible routes and departure time of community shuttles, Sustainability, 2020
    • A sustainable road pricing oriented bilevel optimization approach under multiple environmental uncertainties, International Journal of Sustainable Transportation, 2022
    • Time-of-day pricing for toll roads under traffic demand uncertainties: A distributionally robust simulation-based optimization method, Transportation Research Part C, 2022
    • A prediction-based forward-looking vehicle dispatching strategy for dynamic ride-pooling, IEEE Transactions on Intelligent Transportation Systems, 2024
    • Optimal location of lane-changing warning point in a two-lane road considering different traffic flows, Physica A, 2020

    6. Resilience

    • On the dynamic vulnerability of an urban rail transit system and the impact of human mobility, Journal of Transport Geography, 2024 (Best Paper Award, TRB 2024-AMR10)
    • Vulnerability and resilience of transportationsystems A recent literature review, Physica A, 2021
    • Sustainability evaluation of multi-component subsea transmission system considering failure dependence and maintenance activities, Ocean Engineering, 2024
    • Multi-crowdsourced Data Fusion for Modeling Link-level Traffic Resilience to Adverse Weather Events, International Journal of Disaster Risk Reduction, 2024

    7. Large Language Models

    • ChatGPT as Your Vehicle Co-Pilot: An Initial Attempt, IEEE Transactions on Intelligent Vehicles, 2023
    • Semantic Understanding and Prompt Engineering for Large-scale Traffic Data Imputation using Graph Transformer, Information Fusion, 2024
    • A Survey on Large Language Model-empowered Autonomous Driving, arXiv.2409.14165, 2024
    • AI-Driven Day-to-Day Route Choice, arXiv.2412.03338, 2024
    • CoT-Drive: Efficient Motion Forecasting for Autonomous Driving with LLMs and Chain-of-Thought Prompting, arXiv:2503.07234, 2025

    7. Machine Learning and Prediction

    • Trajectory Prediction for Autonomous Driving Using Spatial-Temporal Graph Attention Transformer, IEEE Transactions on Intelligent Transportation Systems, 2022
    • A Generative Adversarial Network for travel times imputation using trajectory data, Computer-Aided Civil and Infrastructure Engineering, 2021
    • Short-term prediction of urban rail transit origin-destination flow: A channel-wise attentive split-convolutional neural network method, Transportation Research Part C, 2021
    • Time-dependent trip generation for bike sharing planning: A multi-task memory-augmented graph neural network, Information Fusion, 2024
    • Spatiotemporal Fusion Transformer for Large-scale Traffic Forecasting, Information Fusion, 2024
    • A cohesion-based heuristic feature selection for short-term traffic forecasting, IEEE Access, 2019
    • Predicting Station-level Hourly Demand in a Large-scale Bike-sharing Network: A Graph Convolutional Neural Network Approach, Transportation Research Part C, 2018
    • Learning traffic as images: A deep convolutional neural network for large-scale transportation network speed prediction, Sensors, 2017
    • Mapping sidewalk accessibility with smartphone imagery and Visual AI: a participatory approach, Philosophical Transactions A, 2024

    8. Data Analysis

    • Portraying ride-hailing mobility using multi-day trip order data: A case study of Beijing, China, Transportation Research Part A, 2021 (2022 Key innovation in Transportation Sector, Ministry of Transport, China)
    • Exploring competitiveness of taxis to ride-hailing services from a multidimensional spatio-temporal perspective: A case study in Beijing, China, Journal of Transport Geography 2024
    • Understanding user’s travel behavior and city region functions from station-free shared bike usage data, Transportation Research Part F, 2020
    • Identifying users transferring between transportation modes: A stable matching approach, IEEE Transactions on Intelligent Transportation Systems, 2025
    • Spatial-temporal fractal of urban agglomeration travel demand, Physica A, 2020
    • Analysis of Travel Demand between Transportation Hubs in Urban Agglomeration Based on Mobile Phone Call Detail Record Data, ASCE Journal of Transportation Engineering, 2022
    • An interactive city choice model and its application for measuring the intercity interaction, Frontiers in Physics, 2022
    • Exploring the inter-modal relationship between taxi and subway in Beijing, China, Journal of Advanced Transportation, 2018
    • Measuring Taxi Accessibility Using Grid-based Method with Trajectory, Sustainability, 2018
    • Mining crowdsourced trajectory and geo-tagged data for spatial-semantic road map construction, Transactions in GIS, 2022
    • A figure-eight hysteresis pattern in macroscopic fundamental diagrams and its microscopic causes. Transportation Letters, 2015
    • A day-to-day invariant macroscopic fundamental diagrams for probe vehicles, 2018 International Conference on Traffic Engineering and Transportation System. Shenzhen, China, 2018
    • Analysis of vehicle driving styles at freeway merging areas using trajectory data, 25th IEEE Intelligent Transportation Systems Conference (ITSC), Macau, China, 2022
    • Traffic Conflict Analysis at Freeway Interchange Merging Areas: A Joint Model Based on Tobit and Survival Analysis Model, 23rd COTA International Conference of Transportation Professionals, 2023
    • Bus-car mode identification: A traffic condition-based random forests method, ASCE Journal of Transportation Engineering, Part A: Systems, 2020
    • Speed Limit: Obey, or Not Obey? arXiv:2307.12189, 2023
    • Factors affecting injury severity in motorcycle crashes: different age groups analysis using Catboost and SHAP techniques, Traffic Injury Prevention, 2024
    • Home-based Trips Analysis and Households Travel Behavior Case Study of Nablus City, Palestine, World Transport Convention, 2022

    9. Policy

    • Closing the loophole of vehicle ownership restriction: The impact of non-local vehicle restriction on new vehicle registrations and air pollution, Transportation Research Part A, 2024
    • Private vehicle drivers' acceptance of autonomous vehicles: The role of trait mindfulness, Transport Policy, 2024
    • The effect of the ‘yield to pedestrians’ policy on risky pedestrian behaviors: Is it a ‘two-edged sword’? Transportation Research Part A, 2023
    • How to promote the transition from solo driving to mobility services delivery? An empirical study focusing on ridesharing, Transport Policy, 2022
    • Commuters' acceptance of and behavior reactions to license plate restriction policy: A case study of Tianjin, China, Transportation Research Part D. 2017

    10. Review and Perspectives

    • Environmental impacts and emission reduction methods of vehicles equipped with driving automation systems: An operational-level review, Transportation Research Part C, 2025
    • Trajectory data-based traffic flow studies: A revisit, Transportation Research Part C, 2020
    • Automated Vehicle-involved Traffic Flow Studies A Survey of Assumptions, Models, Speculations, and Perspectives, Transportation Research Part C, 2021
    • Shared mobility: Characteristics, impacts, and improvements, Transportation Research Part D, 2021
    • Space Weather Effects on Transportation Systems: A Review of Current Understanding and Future Outlook, Space Weather, 2024
    • Vulnerability and resilience of transportationsystems A recent literature review, Physica A, 2021
    • Special issue on methodological advancements in understanding and managing urban traffic congestion, Transportmetrica A, 2022
    • Guest Editorial: Modeling, Operation and Management of Traffic Mixed with Connected and Automated Vehicles, IET Intelligent Transport Systems, 2024
    • Vehicle Sensor Data-based Transportation Research: Modeling, Analysis, and Management, Journal of Intelligent Transportation Systems, 2019
    • Route guidance strategies revisited: Comparison and evaluation in an asymmetric two-route traffic system. International Journal of Modern Physics C, 2014
    • Research based on high-fidelity NGSIM vehicle trajectory datasets: A review. DOI: 10.13140/RG.2.2.11429.60643, 2017
    • Six Questions on Network-wide Traffic Prediction. DOI: 10.13140/RG.2.2.10498.63681, 2019.9

    11. Others (Selected)

    • A novel one-stage approach for pointwise transportation mode identification inspired by point cloud processing, Transportation Research Part C, 2023
    • Road Intersection Optimization Considering Spatial-temporal Interactions among Turning Movement Spillovers, IEEE Transactions on Intelligent Transportation Systems, 2022
    • Deep Learning Empowered Traffic Offloading Intelligent Software Defined Cellular V2X Networks, IEEE Transactions on Vehicular Technology, 2020
    • Energy-efficient resource allocation for dynamic priority-based in-vehicle mobile-health communications, IEEE Systems Journal, 2020
    • Mobile traffic sensor routing in dynamic transportation systems. IEEE Transactions on Intelligent Transportation Systems, 2014
    • Gating control for a single bottleneck link based on traffic load equilibrium, International Journal of Civil Engineering, 2016
    • Empirical study on the influence of learning ability to individual travel Behavior, Journal of Transportation Systems Engineering and Information Technology, 2009
    • Approximating the minimum distribution of two normally distributed variables each with the same mean and variance. Fifth International Joint Conference on Computational Sciences and Optimization, 2012
    • Introduction to applications of swarm in transportation research, Fourth International Joint Conference on Computational Sciences and Optimization, 2011
    • Delays caused by motorized vehicles unable to clear intersections in China: Graphical analysis. Journal of Central South University, 2013
    • Exploring the relationship between EGG and ordinary driving behavior: A simulated driving study. Journal of Transportation Research Board, 2018

    Other Pages: General Information, Slides and Presentations, List of All Publications

  • broken image

    From this distant vantage point, the Earth might not seem of any particular interest. But for us, it's different. Consider again that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.

    The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds.

    Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves.

    — Carl Sagan