So, how big would an asteroid or planet have to be...

[SaltyNuts]

Before one would no longer have to worry when they jump they might never come down, instead escape into space? Obviously, the moon is to big. What about something half its size? A quarter of its size? Assume I'm talking about an average, 200lb 6'2" ripped guy here like me.

Any thoughts?

Thanks.

 

[IronWing]

We need to know how hard you can kick off (acceleration) and how long it takes you to jump (time between when you start accelerating and the time your feet leave the ground (you go ballistic) so we know how long your acceleration acted on your body.

 

[SaltyNuts]

I dunno IronWing, that's kind of why I was saying just assume an average guy. I have no idea lol. Can you just make a guesstimate? I'm just curious about how big something would have to be. Would something the size of a building be big enough for example? The size of a small city?

 

[Sheep221]

Last impact was pretty bad indeed but we are still around

Giant impact hypothesis


This is the prevailing theory supported by the scientific community. Like the other planets, the Earth formed from the leftover cloud of dust and gas orbiting the young sun. The early solar system was a violent place, and a number of bodies were created that never made it to full planetary status. According to the giant impact hypothesis, one of these crashed into Earth not long after the young planet was created.

Known as Theia, the Mars-size body collided with Earth, throwing vaporized chunks of the young planet's crust into space. Gravity bound the ejected particles together, creating a moon that is the largest in the solar system in relation to its host planet. This sort of formation would explain why the moon is made up predominantly of lighter elements, making it less dense than Earth — the material that formed it came from the crust, while leaving the planet's rocky core untouched. As the material drew together around what was left of Theia's core, it would have centered near Earth's ecliptic plane, the path the sun travels through the sky, which is where the moon orbits today.

 

[SaltyNuts]

Ummmm, I'm not really sure how to respond to that....

 

[dullard]

Ummmm, I'm not really sure how to respond to that....

You don't. He could only read as far as the word "asteroid" before posting, without reading what you were asking about at all. Thus, if you responded to his post, again he would only get 6 words of your response read. Our attention spans are getting shorte hey look a butterfly!

 

[sandorski]

We need a Math genius with the pertinent Physics equation access/knowledge to figure this out. I would refrain from Jumping until we do.

 

[Thebobo]

We need a Math genius with the pertinent Physics equation access/knowledge to figure this out. I would refrain from Jumping until we do.

Ops


Posted from his Android at 20,000 feet

 

[SaltyNuts]

You don't. He could only read as far as the word "asteroid" before posting, without reading what you were asking about at all. Thus, if you responded to his post, again he would only get 6 words of your response read. Our attention spans are getting shorte hey look a butterfly!

LOL!

 

[Sheep221]

You don't. He could only read as far as the word "asteroid" before posting, without reading what you were asking about at all. Thus, if you responded to his post, again he would only get 6 words of your response read. Our attention spans are getting shorte hey look a butterfly!

You know what, it's true, I interpreted question as how big object would have to hit us in order to well, smash us(him) away from earth. Guess I need more coffee.

 

[[DHT]Osiris]

Per the intertubes, it looks like the jumping speed of an average adult male is around 9m/s (assuming at launch moment), for reference, the Earth's escape velocity is 11km/s, and escape velocity of 67P (that asteroid the Rosetta lander touched down on back in '14) is about 1m/s. So far closer to the mass of 67P (10x10^12KG) than Earth. I doubt it scales linearly (9x that amount) but someone who actually knows this stuff may be able to comment.

EDIT: Oh, and the moon's escape velocity is 2.38km/s, so much smaller than the moon as well.

 

[Paratus]

Before one would no longer have to worry when they jump they might never come down, instead escape into space? Obviously, the moon is to big. What about something half its size? A quarter of its size? Assume I'm talking about an average, 200lb 6'2" ripped guy here like me.

Any thoughts?

Thanks.

We need a Math genius with the pertinent Physics equation access/knowledge to figure this out. I would refrain from Jumping until we do.

Science Minister of the Amused FSCK off and Die club here.

The highest standing jump according to google was 5ft 3in.

Ignore air resistance and use newtons equations of motion:

5ft 3in = .5(g)(t^2)
Velocity = g(t) and you get an initial velocity of 18.4ft/s or 5.608 m/s. This is our escape velocity.

The formula for escape velocity is:

M is the mass of our asteroid
R is the radius
G is Newtons gravitational constant

To figure this out we need the average density of an asteroid and we'll assume it's basically a spherical asteroid.

The page has a bunch of asteroid densities.
http://astrostatistics.psu.edu/datasets/asteroid_dens.dat

The average was 2140 kg/m^3
The formula for a sphere is
V= 4/3 PI R^3

The formula for mass is
M = V Density.

So using all of the above I come out with an asteroid with

Mass (M) = 1.2 x 10^15 kg
Radius (R) = 5.1KM

Any larger and you won't be able jump off.

 

[angminas]

Radius of around 20km. We know that you can momentarily outjump gravity on the Earth (9.8 m/s^2), so let's say your maximum initial jumping velocity is 20 m/s. Carme is a moon of Jupiter with a radius of about 23km and an escape velocity of about 28 m/s.

https://en.wikipedia.org/wiki/Carme_(moon)

 

[SaltyNuts]

Wow, thanks Paratus, awesome! So 5.1 KM radious I get - like 3 miles or so. That's not that big! What does that mass equate too, roughly? Any idea?

 

[SaltyNuts]

Whoa, angminas, your 20km # is 4 times the size of Paaratus's number?! And isn't mass the most relevant thing?

 

[angminas]

Whoa, angminas, your 20km # is 4 times the size of Paaratus's number?! And isn't mass the most relevant thing?

I didn't bother to do the heavy math.

 

[Paratus]

Wow, thanks Paratus, awesome! So 5.1 KM radious I get - like 3 miles or so. That's not that big! What does that mass equate too, roughly? Any idea?

I don't know something like 13 million aircraft carriers

 

[Paratus]

Whoa, angminas, your 20km # is 4 times the size of Paaratus's number?! And isn't mass the most relevant thing?

His velocity is 50-60% faster. If his moon was less dense than my average that would also make it larger.

I could have screwed something up too. Although we are both in the same ballpark.

 

[SaltyNuts]

No kidding? 13 MILLION? Wow.

Thanks so much guys!

 

[IronWing]

I don't know something like 13 million aircraft carriers

Shens. Aircraft carriers don't have mass; they float.

 

[SaltyNuts]

I've read it before many times, but it sure does seem gravity is EXTREMELY weak compared to the other forces of nature. 13 million aircraft carriers it takes just to keep you from jumping off. Wow. I wonder why gravity is so weak, and the other forces so strong. The hand of some kind of God, methinks.

 

[DigDog]

i got about 9m/s jumping and 11.100m/s escape velocity on earth, so approximately 1/1233 or the earth's mass.
and you would do a really funny yo-yo effect jump if the gravity was just slightly over that.

 

[Paratus]

I did a google search and a guy on Reddit came up with roughly the same answer.

https://www.reddit.com/r/askscience/comments/q88lw/how_small_would_the_moon_need_to_be_for_someone/

2.5km radius for a 2.4m/s escape velocity (regular guy jumping) and a higher density, (he used the moons average density which is 60% higher than my asteroid average).


So I feel better that I didn't blow it.

 

[Paratus]

Shens. Aircraft carriers don't have mass; they float.

Must be why motorcycles float too.

 

[mxnerd]

Shens. Aircraft carriers don't have mass; they float.

You can float on water too. So you also have no mass?