# The Naked Scientists Forum

### Author Topic: Gravity vs. Apparent Size  (Read 2768 times)

#### Seldomridge

• First timers
• Posts: 1
##### Gravity vs. Apparent Size
« on: 03/08/2005 00:25:03 »
Recently a hoax concerning the close approach of Mars (really happened in 2003) provoked a question.

If Mars could approach earth to a distance that made it appear to be the same visual size as our Moon, would it exert the same gravitational tug on the earth as the Moon does?  For Mars to appear the same size as our Moon, it would have to be a lot farther away from Earth and the Moon is, therefore its gravity would diminish with distance.  On the other hand it is a lot more massive than the Moon so compared to the Moon would exert more of a gravitational pull (if both the same distance from Earth).

I guess what I am asking is...... is there a law in physics that would make rocky planets or moons (assuming both have the same density) exert a equal gravitational tug based on their apparent size?

Secondly,

If you could speed away from Earth close to the speed of light and understanding that Earth time would speed up compared to the time inside the spaceship and, if you could peer back at the Earth with an infinitely powerful telescope (on the spaceship), would you see action back on Earth speed up?  Conversely, what would you see through the telescope if you were traveling towards the Earth near the speed of light?

Autumn Hills Woolens

#### David Sparkman

• Sr. Member
• Posts: 234
##### Re: Gravity vs. Apparent Size
« Reply #1 on: 04/08/2005 04:18:01 »
You would notbe able to see any change in the speed of life on earth. The light reaching your telescope would have to travel further for each frame of the picture, so the transmission of data does not appear to slow down. It does change when you are moving toward the earth as you are living slowly, and the information is traveling a shorter distance each moment. I think that all these laws were made to totally confuse anyone attached to this temporal world.

David

#### simeonie

• Sr. Member
• Posts: 351
##### Re: Gravity vs. Apparent Size
« Reply #2 on: 04/08/2005 23:48:18 »
I would have thought that if you travelled faster than the speed of light (dnt know if it is possible or not but dnt comment on that) and looked from the moon down to earth with a really powerful telescope u would see things that happened before. So you would look back in time. I think

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