Travel Definition and 994 Threads

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...

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...

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...

Hi I'm currently writing a YA novel where the protagonist needs to leave Earth to save his mother. Meanwhile, the protagonist's mother is back on earth. I would prefer if he could be back "instantly". Superluminal traveling is possible in this story. If the protagonists travels at...

Hi all. I was wondering if time is dilated whilst traveling in a stable magnetic field that is generated by the object travelling, and if so, does this vary if you reduce or intensify the magnetic field? Also, what happens if the object is generating two opposing magnetic fields, would...

Homework Statement The coefficient of static friction is 0.604 between the two blocks shown. The coefficient of kinetic friction between the lower block and the floor is 0.104. Force F causes both blocks to cross a distance of 3.44m, starting from rest. What is the least amount of time in which...

Although we can't technically do this currently, what if we could? What would be a reason to send a person on a mission into the future? If Bob travels at near the speed of light from Earth for let's say 5 years and then returns to see Alice. Alice has, and in fact the entire population of Earth...

I read in a so called sci-fi website from my country that as the universe is expanding we may not be able to get to certain galaxies in a possible interstellar travel. That information seems ok for me. But then there was a comment by a reader concluding from the website post that there is coming...

Does light traveling through a fiber optic cable generate any sort of detectable electromagnetic field? Please forgive the stupid question. It’s something that popped into mind recently and google hasn’t adequately answered for me. I’m not a scientist or physicist. :blushing:

Homework Statement If you create a 1 ms light pulse by turning a flashlight on and off, how long will the pulse take to reach the other side of the room 20m away? (in air at standard T and P) what is the length, in m, of the pulse? I realize that light has a wavelength and when you pulse it...

How does the sun emit or radiate its electromagnetic waves? https://imgur.com/odqclja Is it like the first picture where it might be spaces in between the waves or more like the picture under it where the waves are uni formally (I think is the right word) with no space in between them? Or...

Suppose a baseball is hit 3 feet above the ground, and that it leaves the bat at a speed of 100 miles an hour at an angle of 20° from the horizontal. I've got the parametric equations in terms of x and in terms of y, and I have values plotted and a graph sketched. My question is in regards to...

How can we travel back and forth in time? And is it really possible?

I've seen across the internet the explanations of why (ignorind wind) the time an airplane takes to travel from one place to another on Earth is the same regardless of its direction of flight. The explanations usually rely on using reference frames. But I thought of one that I think is more...

Please see my attachment of a recent observation of light traveling through a medium. There is no source, just my observation The packets of light appear to be visible, distinct , moving at different speeds, and display the various colours for each wavelength. Is this normal / possible in a...

I had a bit of a thought experiment the other day, does relativity mean that technically you couldn’t travel faster than the speed of light to the observer. But if you were traveling from Earth to another planet, could you technically be traveling faster than the speed of light relative to the...

Hi. Perhaps it falls into a fallacy similar to the attempt to deny the Second Principle of Thermodynamics, misrepresenting the statistical and probabilistic interpretation. I will also expose what causes me curiosity. My cell phone and the base of the service communicate with each other because...

So an object unaffected by any gravity free floating in space has zero mass. Now could this object reach light speed. Or am I confused?

I need help calculating travel time as a function of distance using drag equation: F_drag = crossection area * density * ballistic coefficient * 0.5 * v^2. Not posted in homework cause it's not, and I don't know how to solve integrals so I could not fill solution attempt box

Hello, I came to this site, with a question in mind. The speed of light. Nothing travels faster than the speed of light. This is a phrase, most of us are familiar with, to some extent. The word "Nothing" has two syllables, "No" & "Thing". There is no thing, that can, travel faster than the...

Photons do not have mass, so why stop at 299700 km/s??

I'm a software developer, no formal astro-physics education, but would like to pose some questions/hypotheticals regarding interplanetary travel, and/or dynamic positioning of Earth orbiting objects using extraterrestrial fuel sources. 1. Asteroid-based hitch-hiking to other planets...

Are there any jobs for nuclear engineering majors that require a lot of travel. International would be preferred. I would just hate to stay in one spot! Any job ideas would help!

The Klingon Empire has opened a travel center in Stockholm, in its quest for world tourist domination. I wonder how many PF'ers work there.

Hey. I know I asked questions about time travel before, but I'm just really interested in it. So, you know the phrase 'Future events cannot effect past events'. Well, in certain movies (eg. Groundhog Day) time keeps resetting, so future events don't effect past events in this scenario. So...

$\tiny{Embry-Brittle \, 12}$ $\textsf{A car, starting from rest, accelerates in a straight line at a constant rate of $\displaystyle 2.0 \frac{m}{s^2}$}$$\textit{How far will the car travel in $10$ seconds}$\begin{align*}\displaystyle \Delta t&=10\\ a&=2\\ d_i&=0\\ v_i&=0\\...

This is a possible science-fiction scenario, and I'm wondering if it is scientifically plausible. If someone wanted to take a one-way trip into future, say 1000 years from now, then SR gives you a possible way to do it without dying of old age: Just hop in a rocket ship, accelerate to nearly...

I hope this is the right forum for this question. Imagine alien tech allows them to travel 1 million light years to Earth instantaneously. No thrust, vector, propulsion was involved. They didn't have to approach the speed of light, with its attendant increase in mass. Having arrived at earth, in...

Who doesn't like to travel to unknown places, away from the hectic city life? Did you experience something great on such trips that is worth sharing? Perhaps Nature had opened up her beauty in front of you, or you have seen something majestic in people's lives that has made you think for a long...

Really silly question, but if we assume that our current science is correct, is it plausible that we can move faster than light in a vacuum? Say, for example, can we make the mass of something less than a photon so it then can it move faster than light in a vacuum. I know this sounds like a...

I've watched a lot of time travel movies, most are just pure sci-fi. Bht some movies use parallel universes to explain the time travel in the plot. Here's where my question comes in: Say if time travel ever was invented, but it created parallel universes when people went back. Would this mean...

So I'm currently on holidays somewhere, and it's one hour ahead of where i live. Since i went on the areoplane and landed to a new country where the time is an hour ahead, this also means i technically landed into the future, right?

Many diagrams show light cones tipping over when closer to a black hole singularity, such that emitted light can have a downwards (negative time) component in the distant observer coordinate frame. e.g this diagram: or this one: or this one: However, other diagrams show that the light...

Now to be brief about this, I found this article at forbes (not to say that forbes is somehow a even remotely scientific journal) So I understand the part about traveling to the future when a person reaches near the speed of light (as a physical object could not reach the very speedlimit itself)...

Near space travels with balloons. http://edition.cnn.com/2015/03/05/tech/balloons-fly-edge-of-space/index.html look at above link. balloons goes just 36 km above Earth surface. but Earth orbit is 100 km away. so my thinking is if we pump oxygen outside near helium balloon artificially when u...

Hi, Can someone please anlayse the visual effects for light travel in the documentary 'Journey to edge of the universe' Especially around the 43:12 and the 1:02:20 mark. Can you also tell me if it is or is not an accurate depiction of what we should be seeing theoretically?

If we need light speed to travel in time and light already have it , so is light traveling in time

I realize this type of question has been asked elsewhere on competitor websites but I want to make it more precise. Usually, the person asks if anything in QM is possible to which the answer is no, for example, a photon cannot have spin 0, hence some things in QM are impossible. But what about...

Hey so from my understanding of Einsteins theory of relativity the closer you travel to the speed of light the slower time is for you, is that right? if it is right does that give to reason that there could be a critical speed past the speed of light for which time for the object traveling at...

Let's assume time travel is possible and we are travelling. We jumped to a TARDIS sort of machine in August 26, 2017 and go to August 26, 2000 then lived there for 4 years until August 26, 2004. So when we come back to August 26, 2017 would we be 4 years older or be the same age we were before...

Let's assume time travel is possible and we are travelling. We jumped to a TARDIS sort of machine in August 26, 2017 and go to August 26, 2000 then lived there for 4 years until August 26, 2004. So when we come back to August 26, 2017 would we be 4 years older or be the same age we were before...

I just wanted to share this idea with other people who may be interested: I watched a PBS Space Time episode about the speed of light more accurately described as the speed of causality. And I Submit! That "time" is simply a interaction between atoms. And though an interaction can be...

I came across an article about one of the many observations that helped to confirm GR. This observation took place during the 1919 total solar eclipse. Stars that were located directly behind the sun could be seen during the total solar eclipse because the gravitational force of the sun bent the...

A thought experiment about the speed of light. Say I build a 600,000 km long tube around the circumference of the Earth at the Equator. The tube's inner diameter is constant at 54.4505 mm. A snooker ball is perfectly manufactured to its lowest tolerance by a special new machine. Each one is...

For some reason, whenever I see these documentaries on space travel, and how NASA explains its projects, they always make it sound like "OMG we'll be able to colonize space MAYBE a million years in the future, with super technology, yadda yadda" and "space travel is so difficult", but aside from...

I've looked up this question on the web, and I've gotten seeming conflicting answers. According to Feynman's path integral - to find the probability of a photon being at A at time 1 and B at time 2 can be determined by taking an integral of the photon traveling over all possible paths. I...

https://arstechnica.com/the-multiverse/2017/07/read-some-seriously-strange-time-travel-stories-from-sci-fis-modern-masters/

Is there any way to travel back in time in reality according to GR? Let me know!

Reading the post below on event horizon of a black hole (BH) got me thinking about the photon sphere of the BH. We all know light will travel around this photon sphere and how light from a source would completely travel back to it's source if one could see it real time, we all know this from...

Yeah, pretty much what the title says. Who has cool ideas for the future of space travel?