为什么天文学家认为，就算达到光速，也到不了宇宙的边缘？【宇宙观察】

If you find several Ads windows appear, just Close the Ads and return to this page, then click the "Download" button again, the Download process will start immediately!

Sorry for showing a lot of ads, we need to make money to pay for the server and keep the tubidy service running smoothly. We apologize for the inconvenience, Your patience is greatly appreciated!