Bright sunny day. Just had a barbecue with friends. I was following some embers floating into the air when I noticed a jet high in the sky. I looked at it wondering where it was going when I saw a small grey dot in the sky above it travelling in the opposite direction. It was much higher and hard to see because it was so high. It passed over the aircraft which was how o realised how high it was. It was difficult to focus on because it was just so high. It travelled in a dead straight line travelling 20 times faster than the plane was moving. It was grey with a dull reflected light. It was approximately 10 times smaller than the aircraft but as it seemed substantially higher I would assume it was of a similar size. The airplane was a passenger jet. I thought it was the space station or something like that but it was the middle of the day and this is not possible. Another possibility was a satellite but I have since been told that only certain types can be seen during the day and that they seem to shine as they catch the light. It did not do this.