I think Colombus ansered that question some centuries ago, you can travel too all AROUND the earth and see for yourself...also there are instruments that show as the Earth is a shpere , sooo even if we forget about the millions of satelites orbiting the Earth ( in order to...orbit you need a sphere) there are ancient instruments to prove it.
Ancient instruments like a gyroscope?
If you get a mechanical gyro-compass and take it aboard an airplane and fly straight east or west by this gyro-compass (turn off all on-board magnetic compasses, GPS etc.) you will eventually arrive at the Antarctic ice wall.
