Over recent years, newspapers have been filled with headlines such as "billions of Earths in the Milky Way alone". But how many Earth-like planets are there really? Join us as we explore all of the different estimates for how many Earths there really are, how each team arrived at their answers, and why they seem to differ so wildy from each other, before finally we'll offer our own answer to this monumental question. Written & presented by Prof David Kipping This video is based on research conducted at the Cool Worlds Lab at Columbia University, New York. You can now support our research program directly here: https://www.coolworldslab.com/support References: ► Youdin, A., 2011, ApJ, 742, 38: https://arxiv.org/abs/1105.1782 ► Catanzarite, J. & Shao, M., 2011, ApJ, 738, 151 https://arxiv.org/abs/1103.1443 ► Dong, S. & Zhu, Z., 2013, ApJ, 778, 11: https://arxiv.org/abs/1212.4853 ► Petigura, E., Howard, A., Marcy, G. W., 2013, PNAS, 110, 19273: https://arxiv.org/abs/1311.6806 ► Foreman-Mackey, D., Hogg., D. W. & Morton, T. D., 2014, ApJ, 795, 12: https://arxiv.org/abs/1406.3020 ► Farr, W. M., Mandel, I., Aldridge, C., Stroud, K., 2014, arXiv:1412.4849: https://arxiv.org/abs/1412.4849 ► Burke, C. J., Christiansen, J. L., Mullally F. et al., 2015, ApJ, 809, 19: https://arxiv.org/abs/1506.04175 ► Silburt, A., Gaidos, E., Wu, Y., 2015, ApJ, 799, 180: https://arxiv.org/abs/1406.6048 ► Traub, W., 2016, ApJ submitted: https://arxiv.org/abs/1605.02255 ► Belikov, R., Stark, C., Batalha, N., et al., 2017: https://exoplanets.nasa.gov/system/internal_resources/details/original/680_SAG13_closeout_8.3.17.pdf ► Garrett, D., Savransky, D., Belikov, R., 2018, PASP, 130, 114403: https://arxiv.org/abs/1810.02847 ► Mulders, G. D., Pascucci, I., Apai, D., Ciesla, F. J., 2018, AJ, 156, 24: https://arxiv.org/abs/1805.08211 ► Hsu, D. C., Ford, E. B., Ragozzine, D., Ashby, K., 2019, ApJ, 158, 20: https://arxiv.org/abs/1902.01417 ► Bryson, S., Coughlin, J., Batalha,