In short, if it appears in the range that the observer can see for less than 65,438+0/24 seconds, it is invisible. If it is necessary to calculate, there must be the information I said before, for example, your angle of view is 90 (ordinary people can't be so few, for the convenience of calculation). A pistol bullet and a building fly 5 meters in front of you in the direction perpendicular to the front. They only need to walk 10 every second. It only takes1100 seconds, and you can't see it, but if they fly one kilometer in front of you at the same speed, they need to walk for two seconds. I believe you can see a building in front of you at 1 km for two seconds, but you can't see the bullet because your eyesight is not that good. So I say it has something to do with the factors mentioned above. Let's talk about an extreme but practical example, the sunny Mid-Autumn Festival. I believe that no one will never see the moon, right? But what is the linear velocity of the bullet's appearance on the moon for you? You can do a rough calculation. Distance to the moon is more than 365,438+0000 kilometers in the center of the earth, so I'll take it as 300,000 kilometers. It will take you about 65,438+0 days to see it return to roughly the same position the next day. Even if it takes 86,400 seconds, I will count it as 90,000 seconds, so that I can calculate that the speed of the moon relative to you is more than 10 km per second. But at this speed, you can watch him for several hours if you like. If we use the sun, we are 65.438+0.5 billion kilometers away from her, and the relative speed is even more horrible. Don't say anything I believe you should understand.
Reply to your supplementary question:
Because the landlord still didn't say anything about the observer's vision, I still assume that the observer's vision can see this object at a distance of 10 meter, with a viewing angle of 90 and a moving direction perpendicular to the front of the observer. Make an isosceles right triangle and you can easily know that this object is within the observer's observation range and needs to walk 20 meters from appearance to disappearance (ignore the size of the object because you have no relevant data description). Then, if the time required for an object to complete this distance does not exceed 1/24 seconds, the observer can't see it, so its speed is at least 20/( 1/24)=480 meters per second, that is, as long as the speed is equal to or greater than 480 meters per second, the observer can't see it.
How do you say that people with 0. 1 second should go to Baidu to receive science first?