If a camera was placed 1 light year away from Earth with a high enough definition, could it be used to spy on events that took place on Earth one year ago? And, if so, could this technique be used to record our past by sending an array of such cameras to the appropriate distance in order to capture momentous events in Earth's history?

Jon King, Swindon, Wiltshire, UK

My limited understanding of science tells me that

a year is the period taken for the earth to orbit the sun, but

seasons are dictated by the tilt of the earth.

Why should there be a link between these?

I recently read that during a change in earth's climate 70 per cent of the creatures became extinct.  If we can predict this can we predict how many species were alive, for example do we know at what point the most species lived on the earth?

Surely it is not now.

Aside from bone and muscle differences, which have already been covered.

For example, someone who grows up without being spun around at 400m/s as the world spins; would they feel as if they were spinning when they set down or entered orbit?

According to me in older generations there were very less earth quakes when compared to the present situations

there were some estimations about earth quakes such that atleast there are 13-17 earth quakes happening month of which 2 of them are major i.e.,a rictor scale reading of 6-7.5

now a days you are able to notice that there are new types of earth quakes happening throughout the world such as TSUNAMI why is the change so . what made rapid increase in earth quakes level ?

even the concept of the 2012 dec 21 include earth quakes ,tsunamis. Is there any alternate to offend from an earth quake other than hiding beneath the tables and benches?

Earth has radius of around 6378 km and our technology are limited to explore only few miles below earth's surface. In that case is there any unknown world exists hundreds of miles below earth surface like in hollywood movie "A Journey to the centre of earth"? Is there any civilization exists which can live at higher temperature found below earth's surface?

One planet's year is defined by how long it takes the planet to complete one orbit around the Sun. So based on the distance from the Sun, one year on Earth is (of course) not the same as one year on Mercury (88 'Earth days') or Neptune (165 'Earth years').

But what if we theoretical were to move to the Sun? What would define one year on a star?

Anders, Norway