• ### Is time traveling possible you think?

190 answers · 6 days ago
• ### What if gravity on earth immediately turned to 200 times greater? Would we survive?

25 answers · 3 days ago
• ### Tension In Elevator?

Best answer: m = mass
a = acceleration
T = tension
g = gravitational acceleration

@ rest or at constant speed
T = m*g

While acceleratin up or braking down
T' = m(g+a)

While acceleratin down or braking up
T'' = m(g-a)
Best answer: m = mass
a = acceleration
T = tension
g = gravitational acceleration

@ rest or at constant speed
T = m*g

While acceleratin up or braking down
T' = m(g+a)

While acceleratin down or braking up
T'' = m(g-a)
7 answers · 17 hours ago
• ### If a spacecraft could use a limitless energy (i.e. fusion) to power it s engines, could it achieve light speed in space?

Best answer: no, for two reasons: 1. limitless energy does not give you reaction mass. To gain velocity, you have to throw away mass, taking advantage of conservation of momentum. More energy means you can toss the reaction mass away at high speed, but it's still not enough to get you very close to c. 2. No, light speed... show more
Best answer: no, for two reasons:

1. limitless energy does not give you reaction mass. To gain velocity, you have to throw away mass, taking advantage of conservation of momentum. More energy means you can toss the reaction mass away at high speed, but it's still not enough to get you very close to c.

2. No, light speed cannot be achieved, as it takes an infinite amount of energy to do that, even neglecting the reaction mass problem above.
9 answers · 2 days ago
• ### Why hasn't a shrink ray been invented?

If all of our atoms were somehow reduced in size by the exact same ratio (that's the tricky part) we would survive it with no problems. We might even feel like the same weight. We'd just have to readjust to our "heavier" environment- and a lot less food- a crumb would feel very filling. Note that... show more
If all of our atoms were somehow reduced in size by the exact same ratio (that's the tricky part) we would survive it with no problems. We might even feel like the same weight. We'd just have to readjust to our "heavier" environment- and a lot less food- a crumb would feel very filling. Note that I didn't ask why an enlarging ray hasn't been invented. I would think that would be a whole lot harder to add mass than to remove it. Correct me if I'm wrong here.
6 answers · 15 hours ago
• ### Why does time exist? I love Albert Einstein’s comment that “the only reason for time is so that everything doesn’t happen at once.”?

Best answer: Entropy and the laws or thermodynamics is why. Entropy goes in only one direction. Entropy is increasing. the universe is becoming more unorganized and chaotic . Time goes in only ONE direction FORWARD.. if the Universe was static. it would not evolve. Whether YOU or ... show more
Best answer: Entropy and the laws or thermodynamics is why.

Entropy goes in only one direction. Entropy is increasing. the universe is becoming more unorganized and chaotic . Time goes in only ONE direction FORWARD.. if the Universe was static. it would not evolve. Whether YOU or Humans beings exist or NOT does NOT matter to the Universe. God DOES play dice with the Universe at subatomic and quark scales of size.. YOU would not exist without time time because the chemical reactions of metabolism and the electrical signals in your nervous system require TIME.. Time is an integral component of the universe. You CANNOT separate the temporal dimension from the spatial dimensions.

Time is an integral component of the Universe. it is N OT a concept invented by human beings HOW WE MEASURE time was invented by human, human beings DID NOT INVENT or create time.
9 answers · 6 days ago
• ### Hey if i drop my phone in the bath while it is on , is there a possibility that i could be electrocuted and die? thanks -dc?

17 answers · 5 days ago
• ### Is methane the chemical/gas that we should be most concerned with when it comes to global warming and climate change?

6 answers · 2 days ago
• ### What laws of physics prevent time travel to the past?

Best answer: One of the most interesting conclusions from special relativity can be best explained by an Einstein quote “the distinction between past, present, and future is a stubbornly persistent illusion”. That seems to drip with the possibility of time travel, but while fascinating, we are prevented from exploiting it by... show more
Best answer: One of the most interesting conclusions from special relativity can be best explained by an Einstein quote “the distinction between past, present, and future is a stubbornly persistent illusion”. That seems to drip with the possibility of time travel, but while fascinating, we are prevented from exploiting it by perhaps the most sacred law in physics - causality cannot be violated.

Einstein’s quote comes from the relativity of simultaneity between different inertial frames in special relativity. Two causally connected events in spacetime happen at different times in different reference frames. If the events are simultaneous in one reference frame, they are not simultaneous in another reference frame. If the events are simultaneous in the ‘present’ of one reference frame, they are not simultaneous in the present of other reference frames. One of the events will occur in the past or future of another reference frame depending on whether it is moving toward or away from the other frame. This negates the idea that there is any notion of absolute past or absolute future, e.g. things are done for everybody and haven’t happened for everybody. We cannot exploit this in relativity because we cannot MOVE FAST enough to violate the causal sequence of the two spacetime events. Special relativity prevents that.

General relativity is a different story. There can be extreme changes in the the geometry of spacetime due to extreme densities and distributions of matter and energy. There are solutions of general relativity, closed time curves and wormholes, that need to be discussed in the context of time travel.

Closed time curves are a similar idea to a closed loop in space, but the closed loop is time not space. These pop up in some solutions of General Relativity such as the Godel metric, which is a contrived metric for a rotating universe, with a contrived distribution of matter and energy. One of the issues with general relativity is that it is ignorant about certain other laws of physics. For instance, general relativity is time symmetric, it does not know about entropy, quantum mechanics, and it has issues with energy conservation. So, while closed time curves are allowed, they are likely non-physical solutions prevented by other laws of physics such as entropy and energy conservation.

Wormholes are always a fun, controversial subject. They are also allowed solutions to general relativity and I’m not going to go into details since I haven’t seen anybody on YA that understands wormhole metrics so it would be a waste of time to go into any detail. Suffice to say that solutions of General Relativity can be found that include wormholes, but the wormholes connect two separate ‘flat’ spacetime regions. General Relativity cannot tell us whether those flat regions are two separate regions of our universe or regions of two separate universes. So, in order to preserve causality, IF somehow a traversable wormhole could be constructed, the requirement for preservation of causality would mean that the two regions are in separate universes and no time travel could actually occur, and hence no causality violations.
13 answers · 6 days ago
• ### Why younger kids are not allowed to sit in front in car ?

Best answer: usually its because the child does not weigh enough to survive a car crash, by this I mean the child has not developed enough to where their internal organs and bones can survive the impact. Thus car manufacturers suggest not having a child in the front seat.
Best answer: usually its because the child does not weigh enough to survive a car crash, by this I mean the child has not developed enough to where their internal organs and bones can survive the impact. Thus car manufacturers suggest not having a child in the front seat.
12 answers · 5 days ago
• ### I have heard it said that dimensional travel may be the key to time travel. Can someone confirm or deny this?

Best answer: Yes it is true. 100% accurate (in theory).
Best answer: Yes it is true. 100% accurate (in theory).
7 answers · 3 days ago
• ### Electrical circuit analysis Kirchoff's laws and ohm's law?

If I connect a 9 v battery, a 30 v battery and a 100 ohm resistor in parallel to each other, what will be the current through the resistor and the potential difference across it??
If I connect a 9 v battery, a 30 v battery and a 100 ohm resistor in parallel to each other, what will be the current through the resistor and the potential difference across it??
4 answers · 5 hours ago
• ### How does the thermal energy of an object differ from its temperature?

5 answers · 2 days ago
• ### What happened without gravity in earth?

Best answer: There wasn't a time when there wasn't gravity here.
Best answer: There wasn't a time when there wasn't gravity here.
10 answers · 4 days ago
• ### What if Time Travel will activate in Japan at 2112 year or 21 century ?

because i was inspired watching Cartoon Doraemon in this many Technology was predicted in Doraemon that was exist in Now
because i was inspired watching Cartoon Doraemon in this many Technology was predicted in Doraemon that was exist in Now
4 answers · 19 hours ago
• ### Do all atoms that exist exist right now?

Best answer: No. Because atoms can decay they are able to change into different atoms. Not only that but if the decay into alpha particles plus other nucleii we have MORE atoms in the future. The same applies to fission. Which can happen. One atom becomes two different and lighter atoms. In the sun we have fusion where... show more
Best answer: No. Because atoms can decay they are able to change into different atoms.
Not only that but if the decay into alpha particles plus other nucleii we have MORE atoms in the future.
The same applies to fission. Which can happen. One atom becomes two different and lighter atoms.

In the sun we have fusion where Hydrogen ceases to exist and a range of other heavier nucleii are created.
6 answers · 3 days ago
• ### Causality Question?

Causality is said to be the relationship between cause and effect, in physics, an effect can never happen before a cause. So does that mean if you went back in time randomly, the fact that you still have memories of future events that have never happened, means you are breaking causality and thus backwards time... show more
Causality is said to be the relationship between cause and effect, in physics, an effect can never happen before a cause. So does that mean if you went back in time randomly, the fact that you still have memories of future events that have never happened, means you are breaking causality and thus backwards time travel is impossible?
5 answers · 2 days ago
• ### How do you calculate the amount of bullet drop in 100 yds?

The weight of the bullet is 2.59196 grams. It’s velocity is 1050 ft. per second The distance the bullet travels is 100 yds. I’m not sure on how to calculate the effect of gravity on the bullet either. If you could I’d like to have some formulas so I could apply them to different distances, with different... show more
The weight of the bullet is 2.59196 grams. It’s velocity is 1050 ft. per second The distance the bullet travels is 100 yds. I’m not sure on how to calculate the effect of gravity on the bullet either. If you could I’d like to have some formulas so I could apply them to different distances, with different weighted bullets, and different velocities. It would be much appreciated.
7 answers · 4 days ago
• ### What is the basic physics behind the reaction forces on a vehicle when it Crosses a bump? How does the wheels gets a reaction force ?

Best answer: The main thing going on is the inertia of the vehicle, ie its reluctance to move upwards when previously it was stationary along the vertical axis. And inertia is quantified as mass (inertia is the general principle but mass gives it a value). So when there is a bump, the road surface effectively accelerates up,... show more
Best answer: The main thing going on is the inertia of the vehicle, ie its reluctance to move upwards when previously it was stationary along the vertical axis. And inertia is quantified as mass (inertia is the general principle but mass gives it a value).

So when there is a bump, the road surface effectively accelerates up, the vehicle has inertial mass, and thus a force is generated on the wheels by F = ma.

Although I suspect this isn't the easiest way analyse what happens and it might be better to use impulse and momentum, but they are slightly trickier concepts.
4 answers · 2 days ago
• ### PHYSICS HELP PLEASEEEE?

Take the mass of the Earth to be 5.98 × 1024 kg. If the Earth’s gravitational force causes a falling 94 kg student to accelerate downward at 9.8 m/s, determine the upward acceleration of the Earth during the student’s fall. Answer in units of m/s
Take the mass of the Earth to be 5.98 × 1024 kg. If the Earth’s gravitational force causes a falling 94 kg student to accelerate downward at 9.8 m/s, determine the upward acceleration of the Earth during the student’s fall. Answer in units of m/s
5 answers · 3 days ago