Travel Definition and 995 Threads

Travel is the movement of people between distant geographical locations. Travel can be done by foot, bicycle, automobile, train, boat, bus, airplane, ship or other means, with or without luggage, and can be one way or round trip. Travel can also include relatively short stays between successive movements, as in the case of tourism.

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  1. J

    I Understanding Relativity: How Moving Objects Experience Near Light Speed Travel

    Light speed is impossible for anything with mass as more and more energy is required with increasing velocity. But this is only to an observer in a different reference frame. To the moving object, in its own reference frame, why would anything change regardless of how close to c it moves?
  2. R

    How Does Space Travel Affect Natural Aging?

    Changes in the body that come from space travel resemble growing older, providing opportunities to perform aging studies on astronauts. https://www.nmn.com/news/how-does-space-travel-affect-natural-aging Any validity to this?
  3. G

    A Can Data Travel Faster Than Light Computation?

    Hi bear with me I have a conundrum I want to ask you. If data traveled many times the speed of light could the results of decrypted cypher message be computed quicker than any system we currently have? For instance if we sent a burst of data at many times the speed of light across the solar...
  4. M

    B Do Photons Decay or Have a Half-Life?

    I don't think this is what is observed, so where is my understanding wrong?
  5. slimak

    B Time Travel Possibility with Two Black Holes Orbiting Each Other

    The reason why I think it could happen is that spacetime is being curved really extremely in black holes and when you draw a chart of spacetime near and in black hole , you can see that time axis is being bend towards the center of black hole and that thing is happening from all sides of the...
  6. Omega0

    Paradox for time travel to the past solved?

    Hello, I am currently reading "The first Fifteen Lifes of Harry August" from Catherine Webb and really like it so far. I did not even read the half or so but there was an interesting idea I would like to discuss about. As far as I understand Harry August does return after dying to the same...
  7. kyphysics

    COVID Could COVID Travel from Car Trunk into Main Car Area from Drive-Up?

    I do curbside/drive-up pick-up service from various businesses. I order on their app. They pack it and when I arrive to the store, they put it in my trunk. No contact. I never have to roll down my window even. I let the groceries (non-refrigerated) or retail goods sit in the trunk for a...
  8. S

    I The Speed of Light: Can it Travel in Opposite Directions?

    Is it really possible for light to travel at different speed in opposite directions? This video seems to say that this is assumed as a fact (with of course Einstein being the one to make the assumption), and that since it is impossible to measure the speed of light in one direction, we really...
  9. B

    Path that requires the least time to travel along

  10. R

    B Distance covered when 22 MeV gamma rays travel through air

    Both alpha and beta radiations can only travel short distances through air as they're not as penetrating as gamma radiations. How long gamma radiations with 22 MeV energy can travel in air? Is it meters, kilometers, miles, etc. Is there a difference between a lower energy gamma ray and a higher...
  11. A

    I Space Travel: Possibilities & Questions

    Is space travel a possibility?
  12. JayJ

    I Why does energy travel in waves?

    Hi all- Im new. Had a weird thought and when researched I only found the answer of bc that’s how we observe it. question. Why does energy travel in waves? Bc that’s how we see it? can anyone explain to me why energy moves in waves and not a straight line? Thanks to all who help me rid...
  13. David Lewis

    B Einstein's Train: Light Travel Time Explained

    https://www.physicsforums.com/attachments/269029 Lightning strikes A and B simultaneously in the Embankment frame. M' sees the flash at B before the one at A. But if the flashes are simultaneous in the Train frame, does M' still see B before A?
  14. K

    Direction of an ionized electron's travel

    Hello! If I have an atom traveling with a given velocity and I ionize it in flight, will the electron remain at the place of ionization, or it will travel at the same speed along with the resulted ion? Thank you!
  15. M

    Can We Travel Close to the Speed of Light?

    Hello! My kid asks if this is theoretical idea is correct and I just don't know this stuff very well: It is impossible to travel at light speed but not impossible to travel just below. So the highest theoretical speed should be: "The distance light has traveled in one second" minus "One Planck...
  16. M

    B Backwards Time Travel: Can We Influence Our Casual Past?

    I've got a good conceptual understanding of relativity (not maths based,) but the one thing which I can't quite get my head around is being able to influcence my casual past. I can picture being able to leave my light cone with faster than light travel, but not to the point where I could go...
  17. DrPython

    Calculate the air pressure needed for a projectile to travel X distance

    Hello! I'm brand new to the physics forum so please excuse any mistakes I make. I'm not even sure if I'm in the right forum section lol. My goal is to create a air cannon to launch a piece of dog food (super overkill) and I have pretty much 0 background in anything post-high school physics. I'm...
  18. J

    I Why Can't Objects Travel Faster Than Light?

    I apologize if this question is in the wrong forum section - but I could not find a proper place for what is a basic question or perhaps a nonsensical one. Is the reason why an object cannot travel faster than the speed of light because the object itself is ultimately made of waves? Is the...
  19. Shubh Goel

    B Time Travel Equation for Case B

    For case B- Conditions: 1. The observer was observing since the time they were in contact. 2. There are only 2 directions for motion: back and forward. 3. Relative velocity is not equal to zero. 4. Bodies are moving away from each other Time difference = t Relative velocity = v Distance between...
  20. I

    Travel time for an accelerating car

    Hi guys, i hope i find the right Sub-Forum. Can you please tell me if i calculated it right. A car speed's up with 5 m/s² to a speed limit of 50Km/h. After it arrived the speedlimit it drives for 30s with the speed of 50km/h. After that it break with a negative acceleration 3.0m/s² to stop...
  21. Benjamin_harsh

    B What's the exact point about time travel?

    It shows theory of time machine proved, what's the exact point that stopping our scientists to create time machine in reality?
  22. P

    What is the maximum depth to which a P-wave ray can travel?

    I've created an excel spreadsheet with the given model in addition to calculating radius of the layer by subtracting depth from 6371. I've calculated Zf. I've also found what I think is vs by doing alpha * (radius column/6371), but that could be wrong. I know I need to find where 20/6371 =...
  23. bland

    I Could many worlds be a solution to time travel paradoxes?

    And also an answer to 'where are the future time travellers?'. Let's say hypothetically that in the future time travel into the past is invented. To me many worlds looks like metaphysics, but it appears to be taken seriously by physicists, therefore, what if after traveling backwards in time as...
  24. C

    Can Time Travel Films Address Ecological Catastrophes and Pandemics?

    I'm seeking sci-fi flicks having to do with traveling back in time to save some ecological disaster and the future. I'm intrigued by this after reading that the ozone is healing so thinking of watching movies like this during the Lockdown. Synopsis: In the middle of the 2020, the ozone gets so...
  25. C

    I How can phonons "travel" if they are excitations of normal modes?

    My understanding is that you can describe the complicated motion of atoms in a crystal as a sum of standing waves (normal modes). A phonon is an excitation of a normal mode in the sense that it increases the vibration amplitude of that normal mode and the energy of that mode by a quantized...
  26. jefals

    B Time Travel: How Does a Fast Electron Experience Sunrise?

    An electron in my gold tooth travels somewhat over half the speed of light. I don't know the math, but let's say I age 10 years for every 1 year for the electron. Suppose we had a way where that electron could trigger a counter each time it "experienced" sunrise. (Let's don't get into how the...
  27. B

    How Long Would Scifi Space Travel Really Take?

    The interesting thing about scifi space travel is that it remains hard even with scifi tech, so long you allow propellant and gravity limits to still exist. In a way it is kind of a good thing, only in that it prevents widespread easy RKV starship use. My question is how long would travel take...
  28. pinball1970

    Time travel using laser technology

    Professor Ron Mallett is claiming that time travel is possible using lasers. I've put this in general for a reason (I was considering putting this in the sci fi section) Article here https://www.cnn.com/travel/article/time-travel-ron-mallett-scn/index.html What I would like to ask is regarding...
  29. M

    A Does Teleportation to Andromeda Equal Time Travel?

    If you could instantaneously teleport from Earth to a planet in the Andromeda galaxy; when you arrive, would you be in what to Earth would be the distant past? Meaning that when you looked at Earth, you would be seeing what it looked like millions of years ago?
  30. FireAP

    Time Travel -- The Flash or Avengers:Endgame?

    Summary:: Which form of time travel would be considered more close to reality: The Flash or Avengers:Endgame? Which form of time travel would be considered more close to reality: The Flash or Avengers:Endgame?
  31. Saptarshi Sarkar

    Time taken for sound to travel between two moving observers

    But the solution should be ##t_1 = \frac a {v_s - v_2}## I assumed the following - 1. I did not consider the frequency as the Doppler shift in frequency was not asked. 2. I did not add the distance the source moved in time ##t_1## to the total distance traveled by the wave as the pulse was...
  32. A

    Why Can a Sound Wave Not Travel Faster than the Average Molecule Speed?

    I am having trouble understanding the following passage in my physics textbook, particularly the bolded sentence: "The speed of sound in a gas is closely related to the rms speed of the molecules of that gas. In a sound wave, the disturbance is passed from one molecule to another by...
  33. Gary Weller

    Will rust travel opposite of gravity?

    I work in the swimming pool industry. We often lock lumber into concrete by hammering hot galvanized nails half way into the lumber for the concrete to grab a hold of. In an "argument" with my boss, I told him if we set the nails at least an inch below the top of the concrete, the rust will...
  34. G

    Travel time of a particle suspended from an elastic string

    Hi, Can anyone please help me with the following: I have found the velocity of projection, no problem, it is v = 2*sqrt(10) Also, in obtaining this value, I have also found the extension in the string when in equilibrium, it is x = 2 Now on to the time of flight. The given answer is: t =...
  35. vicvalis

    I Travel from Mars to Earth question......

    First, i think this is the correct place to ask this question. So the story is that I'm working on a piece of fiction that I want to be as accurate as possible. One part of it involves an object that travels from Mars to earth. This would have been between February 22, 1901 (beginning of...
  36. D

    I Time travel to the Andromeda Galaxy

    Hi, I recently learned that if you can travel at the speed of light, or nearly, you can reach the Andromeda Galaxy within 30 years, due to time dilation and bypassing 2.5 million years on Earth. Is this true?
  37. K

    I Max Time Travel Date: Can We Enjoy Moments From the Past?

    Even if we manage to travel back in time, according to relativity, we could never travel to a moment before we started our journey, right? So in particular I could not enjoy some moments again with a relative that passed away, say 10 years ago?
  38. A

    A Exploring Time Travel Teleportation: Computer Bytes & Radio Signals

    Time travel teleportation can be achieved in small scale experiment in millisecond. Using a computer byte in radio signals. I look forward for comments.
  39. TytoAlba95

    How does the EPSP or IPSP travel towards the axon hillock?

    My concepts so far: EPSP and IPSP are membrane potentials generated due to the opening of ligand-gated ion channels.EPSPs are membrane potentials that are well below the threshold potential, generated due to the influx of Na or Ca ions(depolarisation).IPSP are membrane potentials that are due...
  40. D

    B Does dark matter travel faster than light?

    Summary: Dark matter, the elusive mass that makes up most of the universe, doesn’t interact with light. Is this because it travels faster than light itself? I have been working on the maths and the theory for several months now in order to discover the nature of dark matter. By rearranging and...
  41. J

    I Why Does Wormhole Travel Take Longer Than a 'Regular' Path?

    Hi! I've just read some articles about the fact that wormhole travel would be slower then taking a "regular space time path" between two hypothetical black holes. This stunned me as I always thought the Einstein - Rosen Bridge would be connecting two distant points in space in a more direct...
  42. Aleoa

    Compare travel times for two paths (one longer but lower than the other)

    I'm really sorry, but i don't understand how to solve this problem. Can you give me some help ? This is the picture of the problem:
  43. TerranIV

    I Particles w/ 0 Inertial Mass Traveling Faster than Light?

    I was just curious if there were any known (theoretical) particles with zero inertial mass that don't travel at light speed. Is this even possible?
  44. BobbaD

    I Can Particles Defy Time by Reaching Below Absolute Zero?

    Could a particle be sent back in time on it's world line? Time is defined by events, but at absolute zero, there is no movement or vibration of a particle - does not time cease to pass then at absolute zero for the particle? If the particle was somehow brought below absolute zero, could it be...
  45. A

    What do you think of this FTL/time travel engine?

    So, I have this idea for the FTL engine for artistic purposes and I wanted to ask if anybody could point out it's flaws. I would greatly appreciate if you were willing to discuss them further. It is just a rough summary, so if you want me to disclose more details, ask away. The idea is as...
  46. R

    Projectile motion -- Maximum range it can travel inside a 2m tunnel

    Homework Statement A particle is projected inside a tunnel which is 2 m high and must not hit the side or ceiling of the tunnel. If the initial speed is U show that the maximum range of the particle inside the tunnel You may assume that the maximum range is attained when the projectile just...
  47. A

    B Could you travel using nuclear bombs?

    I have two scenarios. One; imagine that, at the same time as the engine of your ship is ignited, there is also a device detonated inside the ship. If timed correctly, the difference between the two would equal out, right? For now, there's one huge problem and that's making sure the aim is...
  48. B

    B Quantum eraser and time travel

    i don't understand, how does quantum eraser not imply time travel? i firmly don't believe in retrocausality, but it really does seem to imply it . can someone please explain in layman terms? in here paul davies says observers now can "constrain" the past, does this mean our perception of...
  49. mollwollfumble

    I Connection between entropy and time travel?

    My background is that I'm an applied mathematician and engineer, self-taught in GR and QFT. It's an old idea, in some dozen or so SciFi books. But I'm looking for a mathematical framework for handling it. The second law of thermodynamics, that entropy always increases in a closed system, can be...
  50. benorin

    B How do physicists know that the past is immutable?

    I was watching a Science Channel show on time travel (though I don't recall the title) and in this show (I hope I get this right from memory, correct me if need be) they stated without proof that 'if something happened in the past is must have always have happened that way', and when they posit...
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