What is Escape: Definition and 372 Discussions

Atmospheric escape is the loss of planetary atmospheric gases to outer space. A number of different mechanisms can be responsible for atmospheric escape; these processes can be divided into thermal escape, non-thermal (or suprathermal) escape, and impact erosion. The relative importance of each loss process depends on the planet's escape velocity, its atmosphere composition, and its distance from its star. Escape occurs when molecular kinetic energy overcomes gravitational energy; in other words, a molecule can escape when it is moving faster than the escape velocity of its planet. Categorizing the rate of atmospheric escape in exoplanets is necessary to determining whether an atmosphere persists, and so the exoplanet's habitability and likelihood of life.

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  1. P

    Escape velocity from solar system

    Hi. I've been wondering, how could I calculate the escape velocity for a body of mass m which is a certain distance r from the center of the Earth to escape the entire solar system, assuming the distance from the center of mass (aprox. from the sun because it's about 99% of the mass of the solar...
  2. S

    Why is KE = 0 at escape speed?

    Hi guys, how can a spaceship supposedly have zero Kinetic energy at escape speed? If this is the case, then once it has reached the area to escape the gravitational attraction of Earth (till it is very minimal) is it saying that it has zero speed? Wouldn't it start falling back because it is...
  3. M

    Energy required to reach Escape Velocity

    Can anyone help me work out the energy required for a rocket powered craft to reach escape velocity. What I'm looking to find is the amount of fuel (in any measurement) that will need to be burned simultaneously to achieve this for a craft carrying a payload of 5 to 10kg. Any help/links to...
  4. G

    Escape velocity and leaving earth

    Need some help with solving bet Do spacecraft (so we're talking about powered object) have to reach escape velocity in any point of travel to leave Earth and if so, can you prove it by any scientific definition ?
  5. B

    Why photon loss energy when escape from a black hole ?

    Hello all . Why photon increase energy and frequency when falls in gravitational field ? or decrease it's energy when escape from a black hole ?
  6. A

    Calculating Escape Velocity of the Moon

    Homework Statement The gravitational acceleration of the moon is 1.6 m/s^-2. Estimate its escape velocity and explain how you did this? Homework Equations v= square roots(2GM/r) The Attempt at a Solution I have absolutely no idea how to do this question at all
  7. S

    What is the distance needed for a rocket to reach a velocity of 0 on Planet X?

    The escape velocity on Planet X is the speed the rocket needs in order to never fall back down again in a universe in which X is the only object. In order for the rocket to not fall back down, its velocity to never become negative, how far away does the rocket have to be when the velocity is 0...
  8. J

    How close could a tachyon get to a black hole and still escape?

    How close could a tachyon get to a black hole and still escape?
  9. M

    Relativistic escape velocity

    Why is there an inherent presumption imbedded in the field of physics that gravitational force is exempt from the rules of relativity? The presumption is based on the non-relativistic expression for escape velocity: v=(2MG/r)^.5 Thus, with a very large mass or a very small radius...
  10. S

    Speed of light enough to escape black holes ?

    I wad thinking since black holes are so dense ... lights speed would get slow significantly , so isn't it that if you are at light speed ( 3 x 10^8 m/s ) then you might come out of a black hole ? Its the same concept we learn in 10 grade ! Am i right ?
  11. C

    Problem with Escape Velocity given final speed

    Homework Statement The radius of Mercury (from the center to just above the atmosphere) is 2440 km (2440103 m), and its mass is 0.31024 kg. An object is launched straight up from just above the atmosphere of Mercury. (a) What initial speed is needed so that when the object is far from Mercury...
  12. S

    Calculating the escape velocity of a pressurised gas

    Well this question I've had since high school (first year mech), how would i calculate escape velocity of a gas if i know volume, diameter of the hole, pressure, temprature and mass.
  13. H

    Gravitational force & escape velocity

    1- F = mk/r^2 ... k is -ve value ...why ?? please in concise way 2- for escape velocity ... v( inital) = root ( 2gR )... with proof thank u
  14. S

    At what height should a gun be fired for bullet to have escape velocity

    Hello, can you can tell me if this is correct? I thought the height would turn out close to where satellites orbit, but it comes out to about 5.5 million miles away! I was very surprised by this, that's about 20 times further than the moon. Here's what I used Escape velocity: Ve = sqrt(2GM/r)...
  15. D

    How do space shuttles reach escape velocity?

    How are space shuttles accelerated to escape velocity? Would it be possible to build a rocket at home that would be capable of getting into space if it were to use liquid hydrogen and oxygen as fuel?
  16. A

    Escape velocity differential equation

    In a lot of calculus texts, there's an example of an application of differential equations involving escape velocity. They write acceleration is dv/dt but then write it as \frac{dv}{ds}\frac{ds}{dt} That just looks like an application of the chain rule but what is the meaning of dv/ds...
  17. W

    Escape Velocity of Heated Nitrogen: A Scientific Inquiry

    What is the escape velocity of nitrogen heated to 325 K?
  18. W

    What the escape rate of water vapor into space?

    I understand that some water vapor escapes into space but what's the amount say per year?
  19. W

    Escape velocity in the atmosphere

    I have a question on escape velocity. Would a planet with 60% of Earths gravity support a relatively thick atmosphere? It would contain nitrogen, oxygen, water vapor and carbon dioxide. This planet would get the same amount of solar radiation and luminousity the Earth does. Would the gases...
  20. D

    Why can't Light Escape Black Holes?

    If light is transmitted by photons and photons are massless and gravity only affects particles with mass, then why can't light escape black holes' giant gravitational force?
  21. J

    Escape speed Mechanical Energy

    Homework Statement Ok, this really IS my last question here. Again, I have a fairly close answer that isn't right. A 1630-kg communications satellite is released from a space shuttle to initially orbit the Earth at a radius of 9. 106 m. After being deployed, the satellite's rockets...
  22. M

    Calculating the escape speed and gravity of a planet / moon

    Problem: One of the asteroids, Ida, looks like an elongated potato. Surprisingly it has a tiny (compared to Ida) spherical moon! This moon called Dactyl has a mass of 4.20x1016kg, and a radius of 1.57x104 meters, according to Wikipedia. Solve: - Find the acceleration of gravity on the...
  23. M

    Finding Escape Speed on Mars: Advanced Gravitational Potential Energy

    Homework Statement The mean diameters of Mars and Earth are 6.9 10^3 km and 1.3 10^4 km, respectively.? The mass of Mars is 0.11 times Earth's mass. (a) What is the ratio of the mean density of Mars to that of Earth? (b) What is the value of the gravitational acceleration on Mars...
  24. Doofy

    Escape UK: Seeking Physics Job Opportunities in a Beautiful Location

    I've lived in the UK all my life and I'm sick of it, sick of the weather, sick of the people, sick of the culture, sick of the long hours and stressing over irrelevant bull. I'm 24, male if it matters, I have nothing really holding me back apart from having family & friend here, and I want to...
  25. F

    Why are there escape velocities for gravity/

    I know that for a rocket ship to escape Earth's gravity, it must be going at least 17,500 mph, or else it won't go into orbit. For a black hole, light can't escape because a black hole's escape velocity is faster than c. But why is there an escape velocity for objects with mass? Why could...
  26. J

    Why is escape velocity given when total mechanical energy is zero?

    can someone please very briefly explain why the escape velocity of an object is given when the total mechanical energy (KE + potential energy) on an object is zero Thanks
  27. P

    Why Might a Space Probe with High Launch Energy Not Escape Earth's Gravity?

    Hi, A space probe is launched from the equator in the direction of the north pole of the Earth. During launch the energy given to the probe of mass m is E=(3GMm/RE) Deduce that the Space probe will not be able to travel into deep space. That is a past paper question my teacher gave...
  28. B

    Calculating Escape Velocity of a Planetary Body

    Homework Statement Determine the escape velocity of a planetary body that has a radius 5 times greater than its Schwarzschild radius. Homework Equations Schwarzschild radius=(2GM)/c^2 escape velocity=√(2GM/r) The Attempt at a Solution v=√((2GMc^2)/(10GM))=√(c^2/5) Is this...
  29. A

    Escape probability of a particle in a sphere

    how can we use statistical mechanics to find the probability of a particle inside a sphere to escape through a hole on the surface (no potential energy) ? any ideas ??
  30. S

    What temperature does Cl2 need to escape Earth?

    Homework Statement At what temperature will Cl2 molecules have sufficient velocity to escape the Earth’s gravitational pull? The escape velocity from the Earth is 25,000 mph. (Note: Cl2 is diatomic, so you’ll need to double the atomic weight shown on the periodic table.) Cl=35.5g/mol...
  31. S

    Question on delta-v and escape velocity?

    I apologise if this isn't the right place to post this. If I was to calculate the escape velocity of a body, e.g. the Earth which is approx. 11.2km/s, could this then be used as the delta-v in the ideal rocket equation to calculate the mass ratio needed? This would be for both a trip to...
  32. K

    How much force a person must exert to escape the center of the earth?

    Hi I'm new to this forum. I've always wanted to know how much force it would take a person to escape the center of the earth. Let's say someone is buried deep into the Earth's mantle nearing the outer core. How much weight of rock (be specific if you can) would be upon that person's body and how...
  33. marcus

    Distance expansion and escape velocity ( thought experiment )

    Distance expansion and escape velocity ("thought experiment") If you care to, it would help if you would check my arithmetic. I may have made one or more mistakes. Thanks to anyone who can show the conclusion here is wrong. The question came up if you have a pair of kilogram masses and you...
  34. G

    Escape of light perfectly orthogonal to black hole

    I have a fairly decent understanding of black holes, but have always had one curiosity that I haven't found a distinct answer to: If light, through whatever reaction, is emitted inside the event horizon of a black hole such that it is directed in a path exactly orthogonal to the black hole...
  35. M

    Location of minimum change in velocity for orbit escape

    Homework Statement A rocket is in elliptic orbit about the earth. To put it into escape velocity, its engine is fired briefly, changing the rocket’s velocity by deltaV . Where in the orbit, and in what direction, should the firing occur to attain escape with a minimum value of deltav...
  36. J

    Understanding Escape Velocity: What Exactly is It?

    What is escape velocity?
  37. A

    Mass of object in Escape velocity

    Why doesn't the escape velocity depend upon the mass of body?
  38. J

    Escape Velocity of the Milky Way

    Homework Statement In the Solar neighborhood, the Milky Way has a flat rotation curve, with V(r)= Vc where Vc is a constant, implying a mass desnity profile ρ(r) ~ r^-2 Assume there is a cutoff radius R beyond where the mass density is zero. Prove that the velocity of escape from the...
  39. G

    Escape velocity from asteroid

    Homework Statement We assume an asteroid with density similar to earth. An astronaut performs a spot jump of 1 meter. Which is the maximum radius of the asteroid in order to escape the astronaut from the asteroid? Homework Equations Vesc=√2GM/R=R√8ΠGρ/3 The Attempt at a Solution...
  40. P

    Orbits of Satellites-Proportions and Escape Speed

    Homework Statement A missile is launched upward with a speed that is half the escape speed. What height (in radii of Earth) will it reach? a. R/4 b. R/3 c. R/2 d. R e. 2R Homework Equations escape speed=√(2GM/r) The Attempt at a Solution r is inversely proportional to...
  41. T

    Find minimum energy to escape an orbit

    Homework Statement When it orbited the Moon, the Apollo 11 spacecraft ’s mass was 7170 kg, its period was 121 min, and its mean distance from the Moon’s center was 1.87167 × 106 m. Assume its orbit was circular and the Moon to be a uniform sphere of mass 7.36 ×1022 kg. Its orbital speed was...
  42. 2

    How do black holes radiate if nothing can escape?

    Hi. So, as title says, how can black holes radiate if nothing can escape from them?
  43. V

    Solve for Escape Velocity on Mars: Differential Equation Method

    Homework Statement The acceleration of gravity on the surface of Mars is 0.38g. The radius of Mars is 2100 miles. Determine the velocity of a particle projected in a radial direction outward from Mars and acted upon by only the gravitational attraction of Mars by first modeling the motion...
  44. J

    How to calculate mass of fuel needed to escape Earth gravity vs. Mars gravity

    I am trying to determine approximately how much fuel it would take to launch a bi-propellant rocket from Mars and Earth such that they escape each planet's respective gravity. Unfortunately, my orbital mechanics is a little rusty, and the solution I'm getting does not make much sense. Here's...
  45. F

    Cannonball shot off of Earth, Escape velocity, max height

    I'm having some difficulty with a homework problem which states: A cannonball is shot straight up out of a very powerful cannon located at the South Pole and reaches a maximum height of one Earth radius above the surface of the Earth. What was its initial speed? How long did it take to reach...
  46. G

    Deriving minimum escape height and velocity

    Homework Statement At which minimum height atoms or molecules are able to leave Earth’s atmosphere to space? To obtain an approximate estimate use the assumption that molecules can leave if the mean free path, λ, is larger than the scale height H. Write λ and H as a function of height and...
  47. S

    What Minimum Height Fish Must Spot Pelican to Escape?

    Homework Statement If it takes a fish 0.19s to perform evasive action, at what minimum height must it spot the pelican to escape? [Suppose a pelican starts its dive from a height of 15.9 m and cannot change its path once committed] If it takes a fish 0.19s to perform evasive action, at...
  48. B

    Energy to escape gravitational pull

    forgetting the need to enter an orbit, is there a difference in the energy required to escape the Earth's gravity by firing a rocket straight up against firing a rocket on a trajectory? Straight up would be a shorter distance.
  49. K

    Horizontal escape of a projectile

    Homework Statement The problem is attached Homework Equations L=mr^2(dr/dt) V_escape=(GM/R)^.5 E=L^2/(2mR^2)-(GMm)/R=0 The Attempt at a Solution after some work i got: dr/dtheta=((r^3/R)-r^2)^1/2 dont know what to do from here. Thanks.
  50. N

    Can the escape velocity be achieved at any angle?

    So I looked at a neat derivation for what the minimun escape velocity is, and It was pretty clever. Because this is conserved: KE + PE = 1/2 *mv^2 + -GMm/r You can find what the velocity would have to be to get to infinity with zero velocity 1/2 *mvesc^2 + -GMm/r = 1/2 *m(0)^2 +...
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