Why there is no such thing as the past or future but only the present.
Let me explain what I mean about this before you dismiss it as an unacceptable theory.
The past is defined as occurring before and leading up to the time of speaking or writing.
The future is defined as occurring at a later time.
According to these definitions, the past is an instance that has already passed and the future is an instance that's still yet to happen.
Now, let's imagine for a second there is a huge apocalyptic incident that wipes out all life on earth and you with a few other people manage to survive by escaping to planet Mars. A couple hundred years go by and life on earth resurges again with a few plants, animals and later people populating the planet the same way we did this time around.
A couple more years go by and those people on Mars decide it is time to come back home to Earth. But because of the conditions on Mars you all come back looking like this...
When you land on earth, you quickly realize that the people down here don't look the same as you. It's been so long since you changed appearance that you even forgot about it. Now people on earth attack you and call you aliens, here to take over the world. You try to explain to them that you come from the past and you are the same as them but your words fall on deaf ears.
To the people on earth, you come from the future. While as an alien you believe you come from the past.
As much as it is true that you come from the future - a time where the human is much advanced with centuries of experience. It is also true that you come from the past - a time that has passed before this moment in time.
Both arguments are not false depending on who's observing the time. What is true without a doubt though, is the fact that you're both in the present. You are just observing time at different perspectives.
I like to think of time as being stuck in one spot and as the earth rotates it brings along different people and situations. In fact, before the internet or cell phones, it was impossible to keep in touch with friends or family unless you lived in the same spot. The internet and cell phones created the simplest form of time traveling.
The internet created connections to these different time spots to create one presence for the people connected to it. This is a faster and more complex form to the post mail system which operates off sync with the present. Post mails are used to send messages from the present to the future.
Do you think it will be possible to send messages from the future to the present?
Please tell me what you think. I would love to hear other people's perspectives on this.
Thank you for reading!
A special thanks to 
Its a different way of looking at it, but it doesn't take the concept of time itself in consideration whatsoever. The aliens on mars that were humans were by definition from the past because hundreds of years have passed. Both the aliens and the new humans on earth endured the same timeline. The only way for those aliens to be from the past/future is if there was a different timezone that made their experiences longer/shorter compared to those on earth.
Correct but there is also a phenomenon known as 'time dilation', which makes time on Mars move slower than on Earth because the planets don't travel with the same speed. My point regarding time is that it is measured by the observer. For example, the fastest of two runners on a 100m track would see time moving slower than the slower guy who sees it moving fast.